to take dog to the woods or leave at home,

[EleanorReally]

due to be 26 or 27

she will be left for about 4 hours but is not reliable in the house
are the woods likely to be too hot?

A very useful post from @Bupster and so important to watch out for laboured breathing and signs of exhaustion.

It depends on the dog, fit and healthy without predispositions to respiratory issues, with sensible precautions there is absolutely no reason not to walk in the woods in mid 20sC temperatures.
Also a reminder that during hot weather waterways and ponds can quickly become infested with dangerous algae (green or blue? I can't remember which is the dangerous one).
Not a popular concept but true, a really really really really short haircut on a dog is not always helpful for those with dogs that need regular trimming.
I'm not a fan of cooling pads and I agree that bringing the core temperature down quickly is by getting the dog entirely wet.